[Gambas-devel] Interface of gb.opengl.sge

[Tomek]

On 28.03.2013 15:39, Benoît Minisini wrote:
> Le 28/03/2013 16:08, Tomek a écrit :
>> On 28.03.2013 09:53, Benoît Minisini wrote:
>>> Le 28/03/2013 09:24, Tomek a écrit :
>>>> On 28.03.2013 02:41, Benoît Minisini wrote:
>>>>> Hi Tomek,
>>>>>
>>>>> I took a glance at your code, and I strongly suggest the following
>>>>> changes to the gb.opengl.gse interface before you go further.
>>>>>
>>>>> Why these changes? Mainly because I try to make Gambas components have
>>>>> the most similar interfaces as possible, so that the learning curve is
>>>>> lower.
>>>>>
>>>>> By the way, not that there is a design problem too : the MD2 model
>>>>> loading routine only works if the endianness of the CPU is the same as
>>>>> the endianness of the file. You should ensure that if the endianness is
>>>>> different, you swap the binary data accordingly.
>>>>>
>>>>> Now the old interface :
>>>>>
>>>>> GB_DESC Md2ModelDesc[] =
>>>>> {
>>>>>        GB_DECLARE("Md2Model", sizeof(MD2MODEL)),
>>>>>        GB_NOT_CREATABLE(),
>>>>>        GB_STATIC_METHOD("Load", "Md2Model" , Md2Model_Load, "(Name)s"),
>>>>>        GB_METHOD("SetPosition", NULL, Md2Model_SetPosition,
>>>>> "(X)f(Y)f(Z)f" ),
>>>>>        GB_METHOD("DrawFrame", NULL, Md2Model_DrawFrame,
>>>>> "(Frame_No)i(Texture)i" ),
>>>>>        GB_METHOD("DrawInterFrame", NULL, Md2Model_DrawInterFrame,
>>>>> "(Frame_No)i(InterFrame)f(Texture)i" ),
>>>>>        GB_METHOD("GetFramesNo", "i", Md2Model_GetNoFrames, NULL ),
>>>>>        GB_METHOD("GetFrameName", "s", Md2Model_GetFrameName,
>>>>> "(FrameNumber)i" ),
>>>>>        GB_METHOD("Scale", NULL, Md2Model_Scale,
>>>>> "(Scale_x)f(Scale_y)f(Scale_z)f" ),
>>>>>        GB_METHOD("_free", NULL, Md2Model_free, NULL ),
>>>>>        GB_END_DECLARE
>>>>> };
>>>>>
>>>>> The new one I suggest:
>>>>>
>>>>> GB_DESC Md2ModelDesc[] =
>>>>> {
>>>>>        GB_DECLARE("Md2Model", sizeof(MD2MODEL)),
>>>>>        GB_NOT_CREATABLE(),
>>>>>        GB_STATIC_METHOD("Load", "Md2Model" , Md2Model_Load, "(Name)s"),
>>>>>        // 'SetPosition' renamed to 'Move'
>>>>>        GB_METHOD("Move", NULL, Md2Model_SetPosition, "(X)f(Y)f(Z)f" ),
>>>>>        // Three properties to get/set the one coordinate
>>>>>        GB_PROPERTY("X", "f", Md2Model_X),
>>>>>        GB_PROPERTY("Y", "f", Md2Model_X),
>>>>>        GB_PROPERTY("Z", "f", Md2Model_X),
>>>>>        // A virtual object for accessing frame properties and count
>>>>>        GB_PROPERTY_SELF("Frames", ".Md2Model.Frames"),
>>>>>        GB_METHOD("Scale", NULL, Md2Model_Scale,
>>>>> "(ScaleX)f(ScaleY)f(ScaleZ)f" ),
>>>>>        // Maybe you should add ScaleX, ScaleY and ScaleZ properties too.
>>>>>        GB_METHOD("_free", NULL, Md2Model_free, NULL ),
>>>>>        GB_END_DECLARE
>>>>> };
>>>>>
>>>>> GB_DESC Md2ModelFramesDesc[] =
>>>>> {
>>>>>        GB_DECLARE_VIRTUAL(".Md2Model.Frames"),
>>>>>        // Was Md2Model_GetNoFrames
>>>>>        GB_PROPERTY_READ("Count", "i", Md2Model_Frames_Count)
>>>>>        GB_METHOD("_get", ".Md2Model.Frame", Md2Model_Frames_get,
>>>>> "(Frame)i"),
>>>>>        GB_END_DECLARE
>>>>> }
>>>>>
>>>>> // The _get method of Md2Model_Frames is implemented that way:
>>>>>
>>>>> BEGIN_METHOD(Md2Model_Frames_get, GB_INTEGER frame)
>>>>>
>>>>>        // Store the frame number into the object, it will be used
>>>>> immediately
>>>>>        // by the method called on the virtual .Md2Model.Frame object.
>>>>>        // Maybe check that the frame number is valid now.
>>>>>        // And don't forget to add the 'frame' field into the object
>>>>>        // structure.
>>>>>        THIS->frame = VARG(frame);
>>>>>
>>>>> END_METHOD
>>>>>
>>>>> GB_DESC Md2ModelFrameDesc[] =
>>>>> {
>>>>>        GB_DECLARE_VIRTUAL(".Md2Model.Frame"),
>>>>>        // Was 'Md2Model.DrawFrame'
>>>>>        GB_METHOD("Draw", NULL, Md2Model_Frame_Draw, "(Texture)i"),
>>>>>        // Was 'Md2Model.DrawInterFrame'
>>>>>        GB_METHOD("DrawInterFrame", NULL, Md2Model_Frame_DrawInterFrame,
>>>>> "(InterFrame)f(Texture)i"),
>>>>>        GB_END_DECLARE
>>>>> }
>>>>>
>>>>> Tell me what you think about that and if you have questions!
>>>>>
>>>>> Regards,
>>>>>
>>>> Hi Benoit,
>>>>
>>>> Thanks for your suggestions, I will try to do as much a I can using
>>>> devel-api documentation page. It's the best way to learn I think. When
>>>> I'm stuck, I'll ask for your help, ok?
>>>> Question 1 - How do I check endianess of the CPU from component level?
>>> You must read a well known two or four bytes integer value from the file
>>> with fread, and see if you get it swapped or not.
>>>
>>> If you get it swapped, then you know that all binary values must be
>>> swapped.
>>>
>>> You can use the magic identifier at the beginning of the file, but
>>> beware that you must check it byte by byte before reading it as a binary
>>> data.
>>>
>>> Otherwise you may take some files starting with the magic number
>>> inverted as MD2 model files!
>> As I absolutely have no means to test Big-Endianness, I think I'll just
>> put GB.Error("Big Endian not supported yet."), if reading header gives
>> reversed value.
>>
>>
>>>> One more question - what would be the best way to make the class
>>>> creatable - Md2Model_new I suppose, but what should be in that function?
>>>> Can it be empty? Without creatable class I can't make an array of it.
>>> Yes, you must be able to create void models, and manage them in all
>>> functions.
>>>
>>> If a void model must not be used anywhere, you can use the "check hook".
>>>
>>> You declare the check hook in the class description structure with:
>>>
>>> GB_HOOK_CHECK(my_check_function),
>>>
>>> Then 'my_check_function' must be a function taking a pointer to a
>>> Md2Model object and returning an integer different from zero if that
>>> object is invalid. (The interpreter will raise the 'Invalid object'
>>> error).
>>>
>>> Moreover, you must think about implementing boolean operators between
>>> models if it has some sense (merging two models for example). I have no
>>> idea, not being an OpenGL expert, but if you want to implement such a
>>> thing, then a void model must be perfectly valid then.
>>>
>>> Regards,
>>>
>> Is it similar to cquad class in GLU? But Md2Model has no external
>> initiator as quadric do.
> No idea. :-)
>
> But if you have two models, maybe it is possible to create one model
> that is the union of both. But I have no idea if it is possible or
> useful. I just told you so in case.
>
>> I made some changes if file, but cant figure out how to return frame
>> object. File Md2Model.c attached.
> Sorry, I forgot a line:
>
> BEGIN_METHOD(Md2Model_Frames_get, GB_INTEGER frame)
>
>     // Store the frame number into the object, it will be used immediately
>     // by the method called on the virtual .Md2Model.Frame object.
>     // Maybe check that the frame number is valid now.
>     // And don't forget to add the 'frame' field into the object
>     // structure.
>     THIS->frame = VARG(frame);
>     GB_RETURN_SELF();
>
> END_METHOD
>
> Then the Md2Model_Frame_Draw method does not take the frame number as
> argument anymore. It will use 'THIS->frame' internally instead.
>
> Regards,
>
Hi Benoit,
I have problems with understanding how the _get method works. After the 
changes my model seems stuck at frame[0] and I know I have to pass the 
frame number to my model but don't know how.

Thanks,
Tomek.